Issue link: https://iconnect007.uberflip.com/i/1419905
78 PCB007 MAGAZINE I OCTOBER 2021 alternative for expensive point-to-point rout- ing for dense boards. VeCS electrical perfor- mance is discussed in an October 2019 PCB007 Magazine article 6 . (It contains an eye diagram showing simulated layer transition in VeCS at 30 GB/s.) Reducing reflections in transmission lines is one of the areas of focus with VeCS. Tun- ing the impedance of the ver tical trace using, for example, a shielded VeCS slot enables the designer to match the vertical and horizontal impedances of the transmission line. Reliability A VeCS laminate reliability review reported that on testing 370HR, it passed six cycles of 260°C reflow including CAF tests. IST VeCS coupons passed 250 cycles and 19 reflow cycles to 217°C. TCT performance on IST passed 100 cycles and TCT performance on CAF coupons passed 100 cycles (Figure 8a). Figure 8: a) CAF test of three VeCS structures for 1090 hours at 85% RH, 850C at 100 volts; b) resistance change of five VeCS-2 slot structures for 500 cycles of 25 to 150°C. (Source: WUS Printed Circuit Co.)